behave randomly with mysql_change_user.
The test case had to be moved into not_embedded_server.test file,
because SHOW GLOBAL STATUS does not work properly in embedded
server (see bug 34517).
behave randomly with mysql_change_user.
The problem was that global status variables were not updated
in THD::check_user(), so thread statistics were lost after
COM_CHANGE_USER.
The fix is to update global status variables with the thread ones
before preparing the thread for new user.
The problem is that currently there is no way to test the behavior
of the mysql_change_user() function using the mysqltest suite because
there is no internal command for it.
The solution is to introduce a change_user command that can be used
to test aspects of the MySQL client function mysql_change_user().
